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首页> 外文期刊>Mycologia >Isolation and characterization of an endo-(1,4)-beta-glucanase secreted by Achlya ambisexualis
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Isolation and characterization of an endo-(1,4)-beta-glucanase secreted by Achlya ambisexualis

机译：Achlya ambisexualis分泌的内切（1,4）-β-葡聚糖酶的分离和表征

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摘要

Models of wall loosening in fungi and other walled eukaryotes require the action of proteins able to reduce the degree of linkage between components of the wall. In the oomycete Achlya ambisexualis, such a role has been proposed for a suite of endoglucanases that are secreted during branching and during the measurable wall softening associated with osmotic stress. We report here the isolation and characterization of one of these isoenzymes. The enzyme has a molecular weight of 32 kDa, a pH optimum of 6.75, a pI of 4.5, and a temperature optimum of 35 C. It is partially inhibited by sulfhydryl-binding reagents and completely inhibited by the tryptophan-binding reagent NBS. The enzyme has an endohydrolytic mode of action with substrate specificity towards glucans that contain beta-(1,4) linkages, either alone (carboxymethyl cellulose) or as mixed linkage (1,4-1,3)-beta-glucans (e.g., Avena glucan). It does not, however, degrade amorphous insoluble (phosphoric acid swollen) cellulose. Most significantly, the enzyme can also hydrolyze linkages in an Achlya cell wall fraction previously shown to consist of a mixed-linkage (1,4-1,3)-beta-glucan. This property is consistent with the long-standing hypothesis that the branching-related endoglucanases of oomycetes play a role in cell wall loosening.
机译：真菌和其他有壁真核生物中壁松弛的模型需要蛋白质的作用，这些蛋白质能够降低壁各成分之间的键合程度。在卵菌中的Achlya ambisexualis中，已经提出了对于在分支过程中以及在与渗透压有关的可测量的壁软化过程中分泌的一组内切葡聚糖酶的作用。我们在这里报告这些同工酶之一的分离和表征。该酶的分子量为32 kDa，最适pH为6.75，pI为4.5，最适温度为35C。它被巯基结合剂部分抑制，而色氨酸结合剂NBS完全抑制。该酶具有内水解作用模式，对含有β-（1,4）键的葡聚糖具有底物特异性，该葡糖聚糖既可以单独（羧甲基纤维素），也可以作为混合键（1,4-1,3）-β-葡聚糖（例如， Avena葡聚糖）。但是，它不会降解无定形的不溶（磷酸溶胀）纤维素。最重要的是，该酶还可以水解Achlya细胞壁部分中的连接，先前显示该混合壁由混合链接（1,4-1,3）-β-葡聚糖组成。该特性与卵菌的分支相关的内切葡聚糖酶在细胞壁松弛中起作用的长期假设相一致。

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